Herbs with medicinal properties have regained worldwide attention due to their therapeutic effect in the treatment of many chronic diseases. The advantages of herbs are due to their non-toxic nature and specificity to aberrantly expressed molecules. Many of the beneficial effects arise from the antioxidant components of herbs. For example, Achillea fragrantissima has been used to treat viral fever, arthritis and diabetes in the Middle East. In a recent study by Applicant, anticancer properties of extracts from Achillea fragrantissima plant were tested using chronic myeloid leukemia (CML) cell line K562. Achillea fragrantissima extract induced differentiation, inhibited growth and brought about death of K562 cells in a time and concentration dependent manner. Differentiation of K562 cells was associated with clearly identifiable morphological change from a round to a spindle shape. Achillea fragrantissima extract also caused disintegration of K562 cell membrane. Induction of cellular differentiation was followed by terminal maturation and eventual death.
Genetic changes involving DNA rearrangements in pluripotent hematopoietic stem cells inhibit differentiation and result in accumulation of undifferentiated erythropoietic cells in blood (1). CML cells in 95% of patients possess Philadelphia chromosome, a genetic rearrangement resulting from reciprocal translocation between chromosome 9 and 22 involving BCR-ABL (Copland et al., 2005). Every year approximately 5000 new cases of CML are diagnosed in the US. CML is now treated with tyrosine kinase inhibitors (TKIs), such as imatinib, dasatinib, or nilotinib.
Discovery of imatinib (also known as Gleevec), a specific BCR-ABL kinase inhibitor, for the treatment of CML in the late 1990s was considered a medical milestone and since has dramatically improved survival rates (2). Imatinib is highly effective in treating the early stages of chronic myeloid leukemia, but remission induced in advanced phase have been shown to reduce survival (3). A third of patients failed to achieve the desired effect with imatinib and hence were considered resistant (4, 5). The primary cause of imatinib resistance in CML patients was thought to be the mutations in the BCR/ABL kinase domain, clonal evolution and amplification of the BCR-ABL gene (4, 6). T315I mutation of the BCR/ABL tyrosine kinase accounts for 10-15% of clinically relevant CML mutations and licensed tyrosine kinase inhibitors are ineffective against this mutation reduces life expectancy of CML in chronic phase from 10 years to just 22 months (7).
Up to now, there has been considerable focus on the role of ABL-kinase-domain mutations as mediators of resistance to imatinib, thereby encouraging the development of a second generation of TKIs capable of inhibiting these mutant proteins. However, increasingly studies have shown that the mutations do not account for all cases of resistance and have a negligible role in the inability of TKIs to eradicate residual disease in patients who are good responders. More recently, attention has turned to the relative roles of drug bioavailability and drug efflux and drug influx proteins in the development of resistance to imatinib (6). Recent history shows that cancer treatments using small molecule inhibitors targeting specific tyrosine kinases eventually lead to development of resistance by cancer cells.
Thus to overcome drug resistance and relapse of disease, therapy with minimal side effects is highly demanded in the clinical field. In that respect, differentiation induction therapy has attracted universal attention (Koeffler, 1983; Spira and Carducci, 2003).
Differentiation therapy is an alternative approach to CML treatment due to its higher specificity compared to the traditional approaches with cytotoxic drugs (Sell, 2006). The human CML K562 cell line established from pleural effusion of a patient in blast crisis (Lozzio and Lozzio, 1977) has been extensively used as an in vitro model for studying differentiation potential of many compounds (Koeffler and Golde, 1980).
Several differentiation inducing agents such as hemin (Villeval et al., 1983), daunomycin (Tonni et al., 1987), herbimycin A (Honma et al., 1989), phorbol esters (phorbol dibutyrate and phorbol 12-myristate 13-acetate, PMA) (Tetteroo et al., 1984; Alitalo, 1990) and thrombopoietin (TPO) (Rouyez et al., 1997) have been used to induce the erythroid differentiation of K562 cell line. Regardless of these achievements, clinical evaluations of these compounds have not been promising. For instance, clinical use of PMA is not recommended due to its tumor-promoting activity. Thus, universal efforts have been devoted to find new and potent differentiation inducers devoid of general toxicities.
For the above reasons, plants have been the center of focus as a natural source for obtaining novel antioxidant, anti-venom, antifungal, antibacterial and anti leukemic Activity agents with differentiation capability (Shu, 1998). Among plant-derived agents, the daphnane-type diterpene esters such as genkwadaphnin (Yazdanparast and Sadeghi, 2004), genididin, geniditrin and gnidilatin (Stanoeva et al., 2005) possess significant antileukemic activities with major metabolic effects on DNA and protein syntheses (8).
The genus Achillea consisting of about 140 perennial herbs has traditionally been used to treat digestive problems, liver and gall-bladder conditions, menstrual irregularities, cramps, fever, wound healing among others. Recent findings have confirmed several traditional uses on the analgesic, anti-ulcer, choleretic, hepatoprotective and wound healing activities. Of these, A. fragrantissima species has been used as traditional medicine by Middle East countries (9-11). A. fragrantissima extract was shown to possess antiviral activity against herpes simplex-1 virus (HSV), poliomyelitis-1 virus (POLIO) and vesicular stomatitis virus (VSV) (12). Powerful antineuroinflammatory functions of A. fragrantissima extract have been reported recently (13). Mechanistically, strong antioxidant potential of A. fragrantissima extract has been suggested to be responsible for its antibacterial action (14).
In this study Applicant evaluated the anticancer properties of Achillea fragrantissima extract on human CML cell line K562. Applicant's results indicated that Achillea fragrantissima extract can induce differentiation, cell maturation and apoptosis of K562 cells and hence may serve as a safe and effective therapeutic in the treatment of CML.